Explain why hunter-gatherer societies were highly mobile.

Choose the molecule that is described by each phrase. energy used during long activities:

Which best explains how a heat pump can heat a room? cold air from the house is moved through pipes, where it absorbs thermal energy. warm air from outside is pushed into the house to replace the cold air. combustion warms the air when chemical energy is transferred to thermal energy. fuel is used to move a piston, which pushes warm air into the house.

What percentage of light hits earth's surface directly?